Featured Research

from universities, journals, and other organizations

Earth sunblock only needed if planet warms easily

Date:
October 11, 2012
Source:
Pacific Northwest National Laboratory
Summary:
A new computer analysis of future climate change that considers emissions reductions together with sunlight reduction shows that such drastic steps to cool Earth would only be necessary if the planet heats up easily with added greenhouse gases.

Ship exhaust creates long streaks of clouds across the ocean's dark surface, making the sky brighter and reducing the amount of heat trapped in the atmosphere. Some researchers are exploring ways to make clouds brighter to reflect more sunlight back into space.
Credit: Photo courtesy of NASA

An increasing number of scientists are studying ways to temporarily reduce the amount of sunlight reaching Earth to potentially stave off some of the worst effects of climate change. Because these sunlight reduction methods would only temporarily reduce temperatures, do nothing for the health of the oceans and affect different regions unevenly, researchers do not see it as a permanent fix. Most theoretical studies have examined this strategy by itself, in the absence of looking at simultaneous attempts to reduce emissions.

Related Articles


Now, a new computer analysis of future climate change that considers emissions reductions together with sunlight reduction shows that such drastic steps to cool Earth would only be necessary if the planet heats up easily with added greenhouse gases. The analysis, reported in the journal Climatic Change, might help future policymakers plan for a changing climate.

The study by researchers at the Department of Energy's Pacific Northwest National Laboratory explored sunlight reduction methods, or solar radiation management, in a computer model that followed emissions' effect on climate. The analysis shows there is a fundamental connection between the need for emissions reductions and the potential need for some sort of solar dimming.

"It's a what-if scenario analysis," said Steven Smith with the Joint Global Change Research Institute in College Park, Md,, a joint venture between PNNL and the University of Maryland. "The conditions under which policymakers might want to manage the amount of sun reaching earth depends on how sensitive the climate is to atmospheric greenhouse gases, and we just don't know that yet."

The analysis started with computer-based virtual worlds, or scenarios, that describe different potential pathways to reduce greenhouse gas emissions, which limits the amount of heat in Earth system due to greenhouse gas accumulation. The researchers combined these scenarios with solar radiation management, a type of geoengineering method that might include shading Earth from the sun's heat by either brightening clouds, mimicking the atmospheric cooling from volcanic eruptions or putting mirrors in space.

"Solar radiation management doesn't eliminate the need to reduce emissions. We do not want to dim sunlight over the long term -- that doesn't address the root cause of the problem and might also have negative regional effects. This study shows that the same conditions that would call for solar radiation management also require substantial emission reductions in order to meet the climate goals set by the world community," said Smith.

How much sun blocking might be needed depends on an uncertain factor called climate sensitivity. Much like beachgoers in the summer, Earth might be very sensitive to carbon dioxide, like someone who burns easily and constantly slathers on the sunscreen, or not, like someone who can get away with SPF 5 or 10.

Scientists measure climate sensitivity by how many degrees the atmosphere warms up if the concentration of carbon dioxide doubles. Smith said if the climate has a medium sensitivity of about 3 degrees Celsius (5.4 degrees Fahrenheit) per doubling of carbon dioxide, "it's less likely we'd need solar radiation management at all. We'd have time to stabilize the climate if we get going on reducing emissions. But if it's highly sensitive, say 4.5 degrees Celsius (8.1 degrees Fahrenheit) per doubling, we're going to need to use solar radiation management if we want to limit temperature changes."

According to NOAA's August report, Earth's temperature has already risen about 0.62 degrees Celsius (1.12 degrees Fahrenheit) since the beginning of the 20th century as the carbon dioxide in the atmosphere has grown from 290 parts per million to 379 parts per million.

But the atmosphere hasn't reached equilibrium yet -- even if humans stopped putting more carbon dioxide into the air, the climate would still continue to change for a while longer. Scientists do not know what temperature Earth will reach at equilibrium, because they don't know how sensitive the planet is to greenhouse gases.

Further, the study showed that, when coupled with emission reductions, the amount of solar radiation management needed could be far less than the amount generally considered by researchers so far.

"Much of the current research has examined solar radiation management that is used as the sole means of offsetting a doubling of carbon dioxide concentrations. What we showed is that when coupled with emissions reductions, only a fraction of that amount of 'solar dimming' will be needed. This means that potential adverse impacts would be that much lower," said Smith. "This is all still in the research phase. We do not know enough about the impacts of potential solar radiation management technologies to use them at this time."

The study will also help decision-makers evaluate solar reduction technologies side-by-side, if it comes to that. Smith and his coauthor, PNNL atmospheric scientist and Laboratory Fellow Phil Rasch, devised a metric to quantify how much solar radiation management will be needed to keep warming under a particular temperature change threshold. Called degree-years, this metric can be used to evaluate the need for potential sunlight dimming technologies.

Whether such technologies will be needed at all, time will tell.

This work was supported by the non-profit Fund for Innovative Climate and Energy Research.


Story Source:

The above story is based on materials provided by Pacific Northwest National Laboratory. Note: Materials may be edited for content and length.


Journal Reference:

  1. Steven J. Smith, Philip J. Rasch. The long-term policy context for solar radiation management. Climatic Change, 2012; DOI: 10.1007/s10584-012-0577-3

Cite This Page:

Pacific Northwest National Laboratory. "Earth sunblock only needed if planet warms easily." ScienceDaily. ScienceDaily, 11 October 2012. <www.sciencedaily.com/releases/2012/10/121011151433.htm>.
Pacific Northwest National Laboratory. (2012, October 11). Earth sunblock only needed if planet warms easily. ScienceDaily. Retrieved October 31, 2014 from www.sciencedaily.com/releases/2012/10/121011151433.htm
Pacific Northwest National Laboratory. "Earth sunblock only needed if planet warms easily." ScienceDaily. www.sciencedaily.com/releases/2012/10/121011151433.htm (accessed October 31, 2014).

Share This



More Earth & Climate News

Friday, October 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How A Chorus Led Scientists To A New Frog Species

How A Chorus Led Scientists To A New Frog Species

Newsy (Oct. 30, 2014) A frog noticed by a conservationist on New York's Staten Island has been confirmed as a new species after extensive study and genetic testing. Video provided by Newsy
Powered by NewsLook.com
Raw: Hawaii Lava Inches Closer

Raw: Hawaii Lava Inches Closer

AP (Oct. 30, 2014) Aerial video shows the path lava has carved across a portion of Hawaii's big island, threatening homes in the town of Pahoa. Officials say the flow was just over 230 yards from a roadway Thursday morning. (Oct. 30) Video provided by AP
Powered by NewsLook.com
Raw: Hawaii Lava Approaching Village Road

Raw: Hawaii Lava Approaching Village Road

AP (Oct. 30, 2014) The lava flow on the Big Island of Hawaii was 225 yards from Pahoa Village Road on Wednesday night. The lava is slowing down but still approaching the village. (Oct. 30) Video provided by AP
Powered by NewsLook.com
Endangered Carpathian Ponies Are Making a Comeback in Poland

Endangered Carpathian Ponies Are Making a Comeback in Poland

AFP (Oct. 29, 2014) At the foot of the rugged Carpathian mountains near the Polish-Ukrainian border, ranchers and scientists are trying to protect the Carpathian pony, known as the Hucul in Polish. Duration: 02:17 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins